1. Field of the Invention
The present invention relates to a dielectric laminated device that is mainly used for high frequency radio equipment or the like such as a portable telephone.
2. Description of the Prior Art
Recently, as the communication equipment becomes miniaturized, the dielectric laminated device that is advantageous for the miniaturization is often used as a high frequency device. One example of the above described conventional dielectric laminated device will be described below while referring to the drawings.
FIG. 4 is a drawing showing an exploded illustration of a strip line conductor of a conventional dielectric laminated device that is formed by normal screen printing. In FIG. 4, reference numerals 101a, 101b, 101c, 101d, 101e denote dielectric layers, and reference numerals 102a, 102b denote shield conductors, and reference numerals 403a, 403b, 104a, 104b, 104c denote strip line conductors, and reference numerals 105a, 105b, 106a, 106b, 106c, 106d, 106e, 106f denote external conductors.
In the interior of the layered product composed of dielectric layers 101a to 101e, the shield conductor 102a, the strip line conductors 403a, 403b, the strip line conductors 104a, 104b, 104c, and the shield conductor 102b are arranged between the dielectric layers in turn, and furthermore, the external conductors 106a, 106b, 106c, 106e, and 106f in front and on the left and right sides of the layered product connect the shield conductors 102a, 102b and form the ground terminal, and the external conductor 106d on the rear of the layered product connects the common short-circuit ends of the shield conductors 102a, 102b and the strip line conductors 403a, 403b, and becomes the ground terminal, the external conductors 105a, 105b on the left and right sides of the layered product are connected to the strip line conductors 104a, 104b, respectively, and form the input and output terminals.
As for the dielectric laminated device composed as mentioned above, the function thereof will be described below.
The strip line conductors 403a, 403b compose a resonator of the quarter wavelength short-circuit type, and the strip line conductor 104c forms a capacitor by being arranged facing to part of the above described strip line conductors 403a, 403b, and connects the above described resonator of the quarter wavelength short-circuit type, and the strip line conductors 104a, 104b form a capacitor by being arranged facing to part of the above described strip line conductors 403a, 403b, respectively, and function as the input and output terminals by connecting one of the above described strip line conductors 104a, 104b and the external conductors 105a, 105b, respectively. Accordingly, the dielectric laminated device in FIG. 4 functions as a band-pass filter in which the external conductors 105a, 105b are the input and output terminals.
Object of the Invention
However, in such a construction as mentioned above, the edge angle of a side part of the strip line conductor becomes small, and the conductor loss because of the concentration of electric field to the side pointed part becomes large, and therefore, the loss as the filter characteristics also becomes large. xe2x80x9cEdge angle becomes smallxe2x80x9d in the above description will be described by using FIG. 5.
FIG. 5 is one end face view when the conventional dielectric laminated device shown in FIG. 4 is cut by a plane substantially at right angles to the strip line conductors 403a, 403b that have substantially parallel relation. As shown in FIG. 5, the angle of the edge part 1403 of the strip line conductors 403a, 403b is small, and therefore, the concentration of electric field to that edge part 1403 is caused.
When the total of the strip line conductors 403a, 403b is made uniformly thick, and the angle of the edge part is made large in order to solve this problem, the stress applied to the interior of the laminated device at the time of dropping the temperature in the burning process or at the time of solder re-flow or the like becomes large by the difference in the heat expansion ratio between the metal to be the conductor and the dielectric layer. By this increased stress, a crack is caused in the laminated device, and as a result of that, there has been such a problem that the degradation of electric characteristics or the lowering of mechanical strength is caused.
Furthermore, there has been a deviation in the distribution of the current flowing in the strip line conductor 403. That deviation in the distribution of the current will be described by using FIG. 10. FIG. 10 is a figure showing the distribution of the current flowing in the strip line conductor 403a in FIG. 4 that composes the resonator of the quarter wavelength. As shown in FIG. 10, it is apparent that the distribution of the current is large on the short-circuit end side, and small on the open end side. By the way, the thickness of the conventional strip line conductor 403a has substantially been uniform, and therefore, in the strip line conductor 403a, the conductor loss on the short-circuit end side where current is concentrated is bigger than the conductor loss on the open end side. That is, it was equivalent to the resistance the short-circuit end side where current is concentrated is bigger than the resistance on the open end side. Therefore, there has been such a problem that the loss as the filter characteristics is also large. This problem has also been caused similarly in the strip line conductor 403b. 
Furthermore, a similar problem has also been caused in the strip line conductor composing the resonator of the half wavelength. In FIG. 11, the distribution of the current flowing in the strip line conductor composing the resonator of the half wavelength is shown. As shown in FIG. 11, it is apparent that a part where a lot of current flows exists in the central part in the case of the strip line conductor composing the resonator of the half wavelength. The thickness of the conventional strip line conductor has been substantially uniform, and therefore, in the strip line conductor composing the resonator of the half wavelength, the resistance value on the short-circuit end side at the central part has been larger than the resistance value on the open end side, and therefore, there has been such a problem that the loss as the filter characteristics is also large.
The present invention is achieved due to the above described problems, and it is an object thereof to provide a dielectric laminated device in which it is difficult to cause the concentration of electric field to be the source of the increase of the loss of the conductor.
Furthermore, it is an object of the present invention to provide a dielectric laminated device in which the resistance of the strip line conductor is more leveled than that of the prior art.
The 1st embodiment of the present invention is a dielectric laminated device, comprising:
a layered product including a plurality of dielectric layers; and
a plurality of strip line conductors arranged in the interior of the layered product,
wherein the thickness of at least part of the side part of at least one strip line conductor among said plurality of strip line conductors is thicker than that of the central part.
The 2nd embodiment of the present invention is the dielectric laminated device according to 1st embodiment, wherein said at least one strip line conductor forms a resonator of the quarter wavelength where the end is a short-circuit, and the thickness of the side part on the short-circuit end side of the resonator is thicker than that of the central part.
The 3rd embodiment of the present invention is the dielectric laminated device according to 1st embodiment, wherein said at least one strip line conductor forms a resonator of the half wavelength where the end is an open, and the thickness of the side part at a part substantially separated from the open end by quarter wavelength in the wavelength direction of the resonator is thicker than that of the central part.
The 4th embodiment of the present invention is a manufacturing method of a dielectric laminated device, having a layered product including a plurality of dielectric layers; and a plurality of strip line conductors arranged in the interior of the layered product, said method comprising:
a step of forming a strip line conductor in which the thickness of at least one side part is thicker than that of the central part on a specified dielectric layer material, and a step of pressing and laminating another dielectric layer material thereon.
The 5th embodiment of the present invention is a dielectric laminated device, comprising:
a layered product including a plurality of dielectric layers; and
a plurality of strip line conductors arranged in the interior of the layered product,
wherein the thickness of a part having more electric current concentrated is thicker than that of a part having less electric current concentrated, in at least one strip line conductor among said plurality of strip line conductors,
The 6th embodiment of the present invention is the dielectric laminated device according to 5th embodiment, wherein said at least one strip line conductor forms a resonator of the quarter wavelength where the end is a short-circuit, and the thickness on the short-circuit end side of the resonator is thicker than that on the open end side.
The 7th embodiment of the present invention is the dielectric laminated device according to 5th embodiment, wherein said at least one strip line conductor forms a resonator of the half wavelength where the end is an open, and the thickness of a part substantially separated from the open end of the resonator by quarter wavelength is thicker than that of the open end part.
The 8th embodiment of the present invention is a manufacturing method of a dielectric laminated device, having a layered product including a plurality of dielectric layers; and a plurality of strip line conductors arranged in the interior of the layered product, said method comprising:
a step of forming a strip line conductor in which the thickness of a part having more electric current concentrated is thicker than that of a part having less electric current concentrated on a specified dielectric layer material, and a step of pressing and laminating another dielectric layer material thereon.
The 9th embodiment of the present invention is the dielectric layered device according to any one of 1st, 2nd, 3rd, 5th, 6th, 7th embodiments, wherein an inside material and an outside material are different at a part in which the thickness of said strip line conductor is relatively thick.
The 10th embodiment of the present invention is the dielectric laminated device according to 1st embodiment, wherein a plurality of shield conductors are arranged in the interior of said layered product, and at least two resonators of the quarter wavelength where the end is a short-circuit and a strip line conductor facing to part of said resonators of the quarter wavelength where the end is a short-circuit are arranged between said plurality of shield conductors, and the strip line conductor connects said two resonators of the quarter wavelength where the end is a short-circuit to each other and forms a multi-stage filter, and the thickness of part of said resonators of the quarter wavelength where the end is a short-circuit is thicker than that of the other part.
The 11th embodiment of the present invention is Communication equipment, comprising:
a transmitter; and
a receiver,
wherein the dielectric laminated device according to any one of 1st, 2nd, 3rd, 5th, 6th, 7th, 10th embodiments is included as an element.